Silver dye bleach photographic elements and processes for their use

ABSTRACT

A process for the manufacture of a photographic color image by the silver dyestuff bleaching process is provided. The photographic material used in this process comprises on a support at least one silver halide emulsion layer containing a diffusionresistant bleachable image dyestuff and immediately on top of said layer on the side facing the light source, a silver halide emulsion layer free of image dyestuff. After imagewise exposure this material is processed in the presence of a dyestuff bleaching catalyst to give a color image. The color image is produced exclusively through image dyestuffs present in the photographic material prior to the exposure. By the present process color images are obtained wherein the gradation, sensitivity and spectral distribution of the sensitivity have been favorably influenced.

United States Patent Marthaler et al.

[ 51 Mar. 21, 1972 [541 SILVER DYE BLEACH PHOTOGRAPHIC ELEMENTS AND PROCESSES FOR THEIR USE [72] Inventors: Max Marthaler, Marly-le-Petit; Alfred Oetiker, Fribourg, both of Switzerland [73] Assignee: Ciba Limited, Basel, Switzerland [22] Filed: July 20, 1970 [21] Appl. No: 56,597

[5 l] ..G03c 5/52, G03c 7/00 [58] Field of Search ..96/73, 74, 20, 53

[56] References Cited UNITED STATES PATENTS 2,397,452 3/1946 White ..96/74 Primary Examiner-Norman G. Torchin Assistant ExaminerAlfonso T. Sur Pico AttorneyHarry Goldsmith, Joseph G. Kolodny and Mario A. Monaco [57] ABSTRACT A process for the manufacture of a photographic color image by the silver dyestuff bleaching process is provided. The photographic material used in this process comprises on a support at least one silver halide emulsion layer containing a diffusion-resistant bleachable image dyestuff and immediately on top of said layer on the side facing the light source, a silver halide emulsion layer free of image dyestuff. After imagewise exposure this material is processed in the presence of a dyestuff bleaching catalyst to give a color image. The color image is produced exclusively through image dyestuffs present in the photographic material prior to the exposure.

By the present process color images are obtained wherein the gradation, sensitivity and spectral distribution of the sensitivity have been favorably influenced.

13 Claims, 5 Drawing Figures Patentd March 21, 1912 3,650,739

3 Sheets-Sheet 1 3 Sheets-Shet 2 Patented March 21, 1972 3,650,739

3 Sheets-Sheet 5 SILVER DYE BLEACH PHOTOGRAPHIC ELEMENTS AND PROCESSES FOR THEIR USE This invention relates to color photography, especially to processes for the production of color images by the silver dyestuff bleaching process.

A customary material for the silver dyestuff bleaching process contains, on a transparent or reflecting support, a redsensitive emulsion layer dyed with blue-green dye-stuff, on top of this a green-sensitive emulsion layer dyed with a purple dyestuff, and at the very top a blue-sensitive emulsion layer dyed with a yellow dyestuff. Filter layers and other intermediate layers can furthermore be present between these emulsion layers. Such a material is exposed to light, developed and finally processed to give a colored image by bleaching the image dyestuffs which are present as a function of the developed metallic silver and removing the excess silver halide and metallic silver from the material.

The known materials and the processes performed with them display various disadvantages which have not up to now been completely overcome.

If only such an amount of silver halide is employed in the photographic material as is required for the beaching of the dyestuff, a material of completely inadequate light sensitivity is obtained. In general, therefore, a large excess of silver halide is used, a large excess of silver is produced, and only a part of the developed silver is utilized for the bleaching of the dyestuff. A higher light sensitivity is thereby achieved but this is still inadequate because the silver halide emulsion is frequently chemically desensitised by azo dyestuff and, especially, because sensitivity is lost by the dyestuffs absorbing light in the spectral sensitivity region of the emulsion, so that the light is absorbed in the layer and no longer exerts an effect in the depth of the layer.

This last-mentioned effect of so-called optical desensitisation has a disadvantageous effect particularly if the sensitivity range of the emulsion and the absorption range of the dyestuff, whilst lying in the same spectral region, do not fully overlap. If, for example, a layer sensitized with a sensitiser is dyed with an image dyestuff of which the absorption maximum lies at somewhat shorter or longer wavelengths than the sensitising maximum of the sensitiser, the spectral sensitivity distribution is not merely uniformly reduced, but two sensitisation maxima result, with a sensitivity gap lying between them, leading to color distortions.

These disadvantages are overcome according to British Patent specification 421,727 by not dyeing the light-sensitive layer but dividing the layer into an upper (that is to say facing the light source) colorless emulsion layer and a lower nonlight-sensitive layer dyed with image dyestuff. If such a layer is developed, a silver image is obtained in the upper layer, and according to British Patent specification 514,955 the dyestuff of the lower layer can be bleached under the influence of this silver image. This remote bleaching is possible through the dyestuff bleaching catalyst (for example 2,3- diaminophenazine) being activated on the silver, and the ac tivated form migrating to the dyestuff and there bleaching the dyestuff. A very large amount of silver, long bleaching times and energetic bleaching conditions, which lead to undesired color gradations, are needed to carry out this process.

Furthermore the gradation of the images manufactured according to the silver dyestuff bleaching process is as a rule too steep, particularly if the process is carried out in the manner indicated with an excess of silver which is only partially utilized for the dyestuff bleaching. This disadvantage was also recognized at an early stage and is for example, according to German Patent specification 733,728, counteracted by bleaching in the presence of an oxidizing agent. This results in a certain flattening of the color image, but this occurs preferably through lengthening the bottom part of the color gradation curve, that is to say at the expense of the sensitivity; furthermore, instead of obtaining a desirable straight line (linearised) gradation, a color gradation curve which is severely deformed into an S-shape is obtained as a result of the lengthening ofthe bottom part.

Another process for flattening the gradation is proposed in U.S. Pat. No. 2,321,195. According to this, the layer is divided into two layers: a dyed layer with a sensitive emulsion and another dyed layer with a less sensitive emulsion. According to this process, the gradation is again corrected at the expense of the sensitivity.

Other disadvantages result from neighboring layer effects which can often only be controlled with difficulty. Thus, whilst no sufficiently diffusion-resistant dyestuffs were yet available, it was difficult to prevent color distortions through dyestuff diffusion. In U.S. Pat. No. 2,391,198 a material is proposed which contains a separating layer, containing emulsion, between the emulsion layers which are dyed with dyestuffs which are not diffusion-resistant. According to this U.S. patent, the silver developed imagewise in the intermediate layer serves to bleach the dyestuff diffusing out of the adjacent color layers. Without an intermediate layer, the dyestuff diffusing into the adjacent color layer results in color displacements. In an intermediate layer without emulsion, the dyestuff which has diffused remains as a residual color haze even if exposure is carried to the point of whiteness.

Since the process according to this patent specification is carried out in. the absence of dyestuff bleaching catalysts, a significant effect on the bleaching of the dyestuff which has not diffused is rendered impossible.

Processes are furthermore also known (U.S. Pat. No. 2,183,394 and British Patent specification 483,464) which start from colored emulsion layers and colorless emulsion layers which serve to record various color impressions. In this process the colorless layers, after undergoing black and white development, are dyed with image dyestuffs which then assist in the production of the image.

The present invention is based upon the observation that the disadvantages mentioned .above can surprisingly be avoided if an emulsion layer containing a diffusion-resistant image dyestuff and an emulsion layer free of image dyestuff are combined, silver images are developed in both layers, and the image dyestuff is bleached in the presence of a bleaching catalyst, so that in addition to the bleaching by the silver intrinsically present in the layer an additional bleaching through the silver of the adjacent layer occurs. As a result of the combination of bleaching close by, and remote bleaching, an effect is obtained which favorably influences the gradation, sensitivity and spectral distribution of the sensitivity.

The present invention provides a process for the manufacture of a photographic color image by the silver dyestuff bleaching process, wherein a photographic material which comprises, on a support at least one silver halide emulsion layer containing a diffusion-resistant bleachable image dyestuff and immediately on top of said layer on the side facing the light source, a silver halide emulsion layer free of image dyestuff the sensitivity of which latter layer is at least as high as that of the layer containing dyestuff, is exposed imagewise and processed in the presence of a dyestuff bleaching catalyst to give a color image, the color image being produced exclusively through the image dyestuffs present in the photographic material prior to the exposure.

As a result of the colorless emulsion layer lying on the side facing the light source, a situation is achieved wherein the sensitivity of the colorless layer does not suffer optical desensitization" by the image dyestuff.

Preferably, the sensitivities of both layers should be such that the sensitivity of the colorless layer is higher than that of the colored layer. This may be achieved in a simpler manner by dividing a single base emulsion into two parts, adding image dyestuff to one part, and casting the two parts on top of one another. The starting point for the two layers can however also be different emulsions (different gradation and different sensitivity). The higher sensitivity of the colorless emulsion layer may be so adjusted that the color gradation curve is linearised by correction of the shoulder part, that is to say it is made to approach a straight line. The necessary adjustment may be established empirically. Thus thecolor gradation may be corrected without loss of sensitivity or even with a gain in effective sensitivity.

Even if starting from the same base emulsion for both 7 7 V, V V 7 EXAMPLE 1 V layers, less emulsion is required in the colorless layer than in Th th two-layer materials A, B and C, which all contain thecolored layer to achieve at least equally high sensitivity in l i d d ff i h l wer la er and gelatine in the the colorless layer. In order to achieve the desired linearizaupper l are cast t a arent u ort. Material A tion effect, it sufiices in most casesif, in the colorless emulsion contains Silver id i h lower layer l i l B y the amount of Silver halide Cast in P unit r iS contains silver bromide in the upper layer only, and material C justed to be equally high as, or preferably only a fraction of, contains silver bromide in both layers. that in the colored layer, for example 10 to 100 percent. The The dyestuff has the formula H0 8 (1)0113 H300 SIO H optical sensitisation of the two layers which belong together and is used in a transmission density of 2.0. The silver bromide preferably lies in the same spectral region. It is, however, not is optically not sensitized; it is used in an amount of 1.5 g. of necessary for both layers to use the same optical sensitiser. Ag/m. in the lower layers (A and C) and in an amount of 0.5 Thus, for example, the maximum of the two sensitisations can g. of Ag/m. in the upper layers (B and C). The amount of be displaced by a few nm, for example up to i nm, or the gelatine used is such that all layers have a thickness of 2.5 width of the sensitisation ranges can differ from one another. each. Thus the colorless layer can optionally be sensitized with a The three materials are exposed to blue light behind a step sensitiser which displays a very narrow band in the region of 25 wedge and are processed as follows: 6 minutes developer the absorption maximum of the image dyestuff, in order to p-methylarninophenol sulphate 2g. compensate the sensitivity gap, caused optical desensitizaanhydrous sodium mph": 50 tion, which has been mentioned. Additional sensitivities in hydroquinone 6g. other spectral regions can be desirable for the production of anhy f s z Carbonale E- POKaSSIUm l'Ol'nl e g. certain mask ng effects Preferably, however, the same sen wmrsumciemfor 1000 mL sitiser is used in both ad acent layers.

When this description speaks of a colorless or dyestuff-free 2 minutes stopfixing bath emulsion layer, this is to be understood to mean that this emulsion layer is free of image dyestuff. It is however not intended Crystalline sodium thiosulphmc 8- to exclude the layer being able to contain a filter dyestuff, L g? g a I 1 through the presence of which the spectral transmission is glacialawic acid selectively reduced during exposure, and/or the image sharpwutersufficiem f r 1000 ml. ness increased. Such a filter dyestuff lS completely destroyed 4 minutes Soaking or eluted during processing in baths. 20 minutes dyestuff bleaching bath The process according to the invention is suitable for single color and multicolor material. It is however of particular im- 1; (96 q su p Ul'lC ucl strengt m portance in the manufacture of multicolor images, because crymmnesodium hypophosphm Is the requirement of matching the gradations and sensitivities of potassium io i 10 the individual color layers to one another reduces the scope -h x y for variations. A multicolor material contains at least two l ff th water sufl'icient for 1000 ml. silver halide emulsion layers containing image dyestu W1 2 mmutes soakmg the image dyestuffs in the layers being different from one 6minutes silver bleaching bath another, and can contain one or more double layers according to the invention. These double layers can optionally be '2; 96 g? su p uric act strcngl n1 separated from other emulsion layers by intermediate layers, crystalline coppersulphm 20 and these intermediate layers can also contain customary adpotassium bromide 60 ditives such as filter dyestuffs, UV absorbers or oxidizing wfllersumciemfor 1000 agems. 2 minutes soaking.

Photographic transparent material of high color density is of 4 mmutes fi f bath particular interest Composition as for stop-fixing bath.

A preferred three-color material according to the present 8 mmutes Soakmg- I invention has the f ll i Structure; Three color wedges A, B and C, running in the same direction as the original, are obtained and these are measured blluwensmve, colourless behind blue filters.

The gradation curves A, B and C are shown in the graphs in FIG. 1. Here the wedge densities of the exposure wedge (exyellow posure increases from left to right) are plotted on the abscisgmemensime' colourless sac and the density is plotted on the ordinate. This is also the case for the curves in FIGS. 2 to 4. Wedge A is too steep. Wedge B is too flat and only inintemmdiatfllayer (g completely bleached. Wedge C has the desired gradation. It is mdflnsmve' colourless noteworthy that the material C has the same threshold sensitivity as the material A, that the gradations A and C follow a very similar course in the bottom sections, and that the image s pp p q or preferably transparent C above all follows a flatter course relative to image A, as a result of a shoulder correction, and has a linearised gradation.

blue-sensitive, yellow green-sensitive, purple red-sensitive, blue-green Suitable pyrazines, quinoxalines or phenazines are preferably used as dyestuff bleaching catalysts. The image EXAMPLE 2 dyestuffs are as a rule azo dyestuffs. V

The following Examples illustrate the invention, the per- The procedure of Example 1 is adopted, but with the followcentages being by weight. ing differences: The dyestuff has the formula NH a or: I N=NONH-O worm-0 0-NHOO C-HN-Q S0311 NH:

The silver bromide used is sensitized with a green-sensitizer 1Q sitizer/lOO g. of Ag. After the same processing as in Example and the exposure is carried out with green light. The three resulting color gradations can be seen from the graphs in FIG. 2.

As regards curves A, B and C, the same is true as in Example 1.

Similar results are obtained if instead of the dyestuff bleaching bath indicated, bleaching is carried out for 8 minutes in a bath which contains 70 ml. of 37 percent strength hydrochloric acid, 50 g. of potassium bromide, 80 g. of thiourea and mg. of 2-amino-3-hydroxy-phenazine per liter.

EXAMPLE 3 A 2.5 a thick layer with silver bromide (1.5 g. of Ag/m?) sensitized towards red light and a blue-green dyestuff of formula H 0 5 -5 0 B H; 0

(transmission density 2.0) is cast onto a transparent support. The material is divided into three parts (A, B, and C).

A: A 2.5 [1. thick gelatine layer is cast onto a part of the material.

B: A 2.5 p. thick layer which contains completely identically sensitized silver bromide (0.5 g. of Ag/m?) is cast onto another part of the material.

C: A 2.5 a thick layer which contains completely identically sensitized silver bromide (1.0 g. of Ag/m?) is cast onto a third part of the material.

After exposure to red light behind a step wedge and the usual processing analogously to Example 1, the three color images A, B and C are obtained. Whilst the colorless emulsion layer results in a considerable gain in sensitivity no optimum linearisation of the gradation is as yet achieved, as can be seen from FIG. 3. The shoulder correction found in curves B and C relative to the gradation curve A shows that here again one is dealing with silver halide emulsion layers of which the sensitivity is higher than that of the layer containing the dyestuff. The conditions chosen are here however not an optimum, so that the linearisation is not complete.

EXAMPLE 4 The procedure of Example 3 is adopted, but with the difference that the silver bromide of the color layer and the silver bromide of the covering layer are sensitized in different ways, with the same sensitizer being employed in different amounts.

A red-sensitizer of formula is used for sensitising the silver bromide in all layers, and in particular the silver bromide of the color layer is sensitized with 80 mg. of sensitiser/ 100 g. of Ag, and the silver bromide of the colorless layer is sensitized with only 40 mg. of senemulsion layer which is free of image dyestuff has a higher 3, the three images A, B and C are obtained. It can be seen from the gradation curves of FIG. 4 that compared to the control experiment ('A) both a gain in sensitivity and a linearisation effect are achieved through a covering layer with 0.5 g. of Ag/m. (B) and even more so by a covering layer with 1.0 g. of Ag/m? (C).

EXAMPLE 5 A material is cast using the following layer arrangement: 9 protective layer 8 AgBr, blue-sensitive 7 AgBr, blue-sensitive yellow dyestuff as in Example I 6 intermediate layer 5 AgBr, green-sensitive 4 AgBr, green-sensitive purple dyestuff as in Example 2 3 intermediate layer 2 AgBr, red-sensitive 1 AgBr, red-sensitive blue-green dyestuff as in Example 3 support, transparent.

Only the protective layer (9) is cast with a thickness of 1.5 p; all other layers (1 to 8) are cast with a thickness of 2.5 4. each. The material is exposed to white, blue, green and red light and is processed as in Example 1. Measurement of the color wedges shows that all colors and tonal values are reproduced better than in the case of photographic material which does not contain any silver bromide intermediate layers.

EXAMPLE 6 The procedure of Example 1 is adopted, but with the following differences:

The layer support is not transparent but opaque white. The image dyestuff has the formula (3) and is used at a reflection density of 2.0. The silver bromide used is sensitized with a red sensitizer; it is used in an amount of 0.9 g. of Ag/m. in the lower layers (material A and C) and in an amount of 0.45 g. of Ag/m. in the upper layers (material B and C). The exposure is carried out with red light. The three color gradations obtained can be seen from the graph in FIG. 5.

The same can be said regarding curves A, B and C as in Example 1.

We claim:

1. A process for the manufacture of a photographic color image by the silver dyestuff bleaching process, wherein a photographic material which comprises on a support at least one silver halide emulsion layer containing a diffusion-resistant bleachable image dyestuff and immediately on top of said layer on the side facing the light source, a silver halide emulsion layer free of image dyestuff, the sensitivity of which latter layer is at least as high as that of the layer containing dyestuff, is exposed imagewise and processed in the presence of a dyestuff bleaching catalyst to give a color image, the color image being produced exclusively through image dyestuffs present in the photographic material prior to the exposure.

2. A process as claimed in claim 1, wherein the silver halide sensitivity than that of the silver halide emulsion layer containing image dyestuii.

3. A process as claimed in claim 1, wherein the sensitivity of the silver halide emulsion layer which is free of image dyestuff is so adjusted that the color gradiation curve is linearized through correction of the shoulder part.

4. A process as claimed in claim 1;whe reiri the silver halide emulsion layer which contains image dyestuff and the adjacent silver halide emulsion layer above it which is free of image dyestuff are optically sensitized in the same spectral region.

5. A process as claimed in claim 1, wherein the silver halide emulsion layer which contains image dyestuff and the top adjacent silver halide emulsion layer which is free of image dyestuff, are optically sensitized with the same sensitizer.

6. A process as claimed in claim 1, wherein the image dyestuff comprises a bleachable azo dyestuff.

7. A process as claimed in claim 1, wherein a pyrazine, quinoxaline or phenazine is used as the dyestuff bleaching catalyst.

8. A process as claimed in claim 1, wherein the dyestuff bleaching catalyst is present in a photographic processing bath.

9. A process as claimed in claim 1, wherein the color bleaching catalyst is present in a layer of the photographic material which is to be processed.

10. A process as claimed in claim 1, wherein the layer which is free of image dyestuff contains l0 to percent of the amount of silver halide of the layer containing image dyestuff.

11. A process as claimed in claim 1, wherein the photo graphic material contains at least two silver halide emulsion layers containing image dyestuff, the image dyestuffs being different from one another,

12. A process as claimed in claim 1, wherein the photographic material comprises. in order, a support layer; a redsensitive layer with a blue green image dyestuff; a red-sensitive layer free of image dyestuff; an intermediate layer; a greensensitive layer with a purple image dyestufi; a green-sensitive layer free of image dyestuff; a yellow filter layer; a blue-sensitive layer with a yellow image dyestuff; a blue-sensitive layer free of image dyestufi.

13. A process as claimed in claim 1, characterized in that the photographic material is transparent material of high color density. 

2. A process as claimed in claim 1, wherein the silver halide emulsion layer which is free of image dyestuff has a higher sensitivity than that of the silver halide emulsion layer containing image dyestuff.
 3. A process as claimed in claim 1, wherein the sensitivity of the silver halide emulsion layer which is free of image dyestuff is so adjusted that the color gradiation curve is linearized through correction of the shoulder part.
 4. A process as claimed in claim 1, wherein the silver halide emulsion layer which contains image dyestuff and the adjacent silver halide emulsion layer above it which is free of image dyestuff are optically sensitized in the same spectral region.
 5. A process as claimed in claim 1, wherein the silver halide emulsion layer which contains image dyestuff and the top adjacent silver halide emulsion layer which is free of image dyestuff, are optically sensitized with the same sensitizer.
 6. A process as claimed in claim 1, wherein the image dyestuff comprises a bleachable azo dyestuff.
 7. A process as claimed in claim 1, wherein a pyrazine, quinoxaline or phenazine is used as the dyestuff bleaching catalyst.
 8. A process as claimed in claim 1, wherein the dyestuff bleaching catalyst is present in a photographic processing bath.
 9. A process as claimed in claim 1, wherein the color bleaching catalyst is present in a layer of the photographic material which is to be processed.
 10. A process as claimed in claim 1, wherein the layer which is free of image dyestuff contains 10 to 100 percent of the amount of silver halide of the layer containing image dyestuff.
 11. A process as claimed in claim 1, wherein the photographic material contains at least two silver halide emulsion layers containing image dyestuff, the image dyestuffs being differeNt from one another.
 12. A process as claimed in claim 1, wherein the photographic material comprises, in order, a support layer; a red-sensitive layer with a blue green image dyestuff; a red-sensitive layer free of image dyestuff; an intermediate layer; a green-sensitive layer with a purple image dyestuff; a green-sensitive layer free of image dyestuff; a yellow filter layer; a blue-sensitive layer with a yellow image dyestuff; a blue-sensitive layer free of image dyestuff.
 13. A process as claimed in claim 1, characterized in that the photographic material is transparent material of high color density. 